Admin Core Eva Nogales PROJECT SUMMARY/ABSTRACT Visualizing the structures of biological molecular machines is crucial for a mechanistic understanding of cellular function. While X-ray crystallography can provide structures for some of these complexes, crystallization precludes general applicability, especially when the amount of sample is limited or the sample is heterogeneous. Cryo-EM is ideally suited to study large assemblies, in multiple states, and using minute amounts of sample. This methodology has just entered a new era with the use of high-end electron microscopes coupled to new direct electron detection cameras that is leading to higher resolution and faster turn-around of structures. These new capabilities rely on very expensive equipment and associated service contracts that make them practical only in the context of a group of investigators that can share costs. Equally importantly, the use of this equipment requires dedicated personnel to provide daily up-keep and high-level training for a large number of users. This personnel requirement extends beyond the microscope and its auxiliary instruments, to IT support personnel who maintain the hardware and software required to handle and process the large influx of data generated by the new detectors operated in automatic mode. As the sophistication of the microscopes and the image analysis increases, and the applicability of the technique expands, a community of scientists with exceptional expertise and frequent intellectual exchanges is required to make cryo-EM research effective, and increase productivity and impact. These exchanges are particularly important at a junction when a significant influx of new researchers and biological systems are coming into the cryo-EM field from other areas in biochemistry and structural biology. These researchers benefit tremendously from existing expertise in cryo-EM around them, while they can provide invaluable biochemical help to traditional researchers in the cryo-EM field that are in the process of expanding their systems of studies and become limited by the availability and behavior of the sample. This administrative core supports all different needs of the participating members, and promotes collaboration and exchanges among them, so that the overall outcome is greater than the sum of the parts. In addition to the four projects and technical Core that constitute the sections of this proposal, support extends to a significant number of associated, independently funded projects in Berkeley that include a substantial level of electron microscopy-based research and rely to some extent on resources supported by the PPG. Furthermore, the support provided by the administrative core also allows the participating members to get involved in collaborations with other investigators concerning projects that at various times may need to complement research with advanced EM capabilities not available elsewhere on Campus or at LBNL, or often to explore new directions. The supported infrastructure facilitates exploratory studies that sometimes become more significant projects, substantially increasing productivity beyond the official research components.